Positioning apparatus and charged-particle-beam exposure apparatus

ABSTRACT

A positioning apparatus including a movable member for transmitting a driving force in a driving-axis direction to a stage, a first electromagnet for driving the movable member in the driving-axis direction by forming a magnetic path between the movable member and the first electromagnet and generating first magnetic flux, and a second electromagnet, which is positioned away from the first electromagnet and arranged in an overlapping direction, for driving the movable member in the driving-axis direction by forming a magnetic path between the movable member and the second electromagnet and generating second magnetic flux having an inverted polarity from the first magnetic flux.

This application is a divisional application of copending U.S. patentapplication Ser. No. 10/693,104, filed Oct. 27, 2003.

FIELD OF THE INVENTION

The present invention relates to a positioning technique, and moreparticularly, to a positioning technique that can be applied to asemiconductor manufacturing apparatus, such as a charged-particle-beamexposure apparatus, which performs pattern drawing using acharged-particle beam.

BACKGROUND OF THE INVENTION

In a semiconductor manufacturing process, lithography is employed as atechnique of drawing patterns on a wafer. In lithography, variouspatterns formed on a mask are demagnified and transferred to a waferusing light beams. The mask patterns used in the lithography requireextraordinary precision. A charged-particle-beam exposure apparatus isemployed to form such mask patterns. A charged-particle-beam exposureapparatus is also used for directly drawing patterns on a wafer withoutusing a mask.

Charged-particle-beam exposure apparatuses include a point-beam type,which irradiates a spot-like beam, and a variable-rectangular-beam type,which irradiates a beam having a variable rectangular cross section.Regardless of the configuration, the charged-particle-beam exposureapparatus generally comprises an electron gun unit for generating acharged-particle beam, an electron optical system for introducing thebeam generated by the electron gun to a sample, a stage system forscanning the entire surface of the sample relative to the electron beam,and an objective deflector for positioning the electron beam on thesample surface with high precision.

A charged-particle beam has an extraordinarily high response. Therefore,rather than improving the mechanical and regulatory characteristics ofthe stage, it is a general procedure to adopt a system that measures anerror in the posture and position of the stage and feedbacks the errorto positioning of the beam by a deflector which causes acharged-particle beam to scan.

The stage is provided in a vacuum chamber and constrained not to causemagnetic field fluctuation that influences the positioning of acharged-particle beam. For this reason, conventionally, all that isrequired is for the stage to move in a two-dimensional direction. Thestage is configured with limited contact-type components, e.g., arolling guide, a ball screw actuator, or the like. Therefore, theconventional contact-type components raise problems of lubrication anddust generation. To cope with these problems, the conventional art hasproposed a construction shown in FIG. 1, which employs electromagnets(1, 2) as a driving element of the XY stage. Japanese Patent ApplicationLaid-Open No. 11-194824 discloses a non-contact six-degree-of-freedomstage mechanism which employs electromagnet actuators and magneticshields. The method disclosed in this document allows less fluctuationof leakage flux and assures a highly immaculate environment. Therefore,it is applicable to a positioning apparatus in a vacuum environment andenables highly precise positioning operation.

Higher precision in exposure operation and higher speed in stage drivingare further demanded to improve a throughput of the exposure apparatus.However, to meet such demands, the non-contact six-degree-of-freedomstage mechanism employing electromagnet actuators and magnetic shields,which is disclosed in the aforementioned document, raises a problem of acomplicated structure of the magnetic shield portion. In other words,due to the massive structure of the magnetic shield portion, the weightof the movable portion of the stage increases. Therefore, it hasconventionally been difficult to achieve high acceleration/decelerationof the stage and high-speed positioning at the cost of the servorigidity of the driving system which includes the above-describedcomponents.

SUMMARY OF THE INVENTION

The present invention has been proposed in view of the conventionalproblems, and has as its object to provide a positioning apparatuscomprising a mechanism for reducing generation of leakage flux. Such apositioning apparatus is realized by simplifying the magnetic shieldmechanism. As a result, it is possible to realize weight reduction of aprecision-motion substrate stage, high acceleration/deceleration of thestage, which mounts the precision-motion substrate stage, and high-speedpositioning control.

To solve the above problem, a positioning apparatus according to thepresent invention mainly has a movable member for transmitting drivingforce in a driving-axis direction to a stage, a first electromagnet fordriving the movable member in the driving-axis direction by forming amagnetic path between the movable member and the first electromagnet andgenerating first magnetic flux, and a second electromagnet, which ispositioned away from the first electromagnet and arranged in anoverlapping direction, for driving the movable member in thedriving-axis direction by forming a magnetic path between the movablemember and the second electromagnet and generating second magnetic fluxhaving an inverted polarity from the first magnetic flux.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1 is a diagram illustrating a construction of a conventionaldriving mechanism;

FIG. 2A is a diagram illustrating a construction of a one-axis drivingmechanism having an electromagnet unit as a driving source;

FIG. 2B is an explanatory view of a current control circuit whichcontrols magnetic flux of electromagnets;

FIGS. 3A and 3B are explanatory views of a magnetic flux distribution ofelectromagnets;

FIG. 3C is an explanatory view describing a positional relation ofelectromagnets and an I core;

FIG. 4 is a diagram illustrating a modification of an I core;

FIG. 5 is a diagram illustrating a construction of a two-axis drivingmechanism having an electromagnet unit as a driving source;

FIG. 6 is a diagram illustrating a construction of a two-axis drivingmechanism having an electromagnet unit as a driving source;

FIG. 7A is a diagram illustrating a construction of a six-axis drivingmechanism having an electromagnet unit as a driving source;

FIG. 7B is an explanatory view describing a configuration of a sideplate constituting a center slider;

FIG. 7C is an explanatory view describing a relation between a drivingunit and a movable member;

FIG. 8 is a diagram showing the overall construction of aprecision-motion substrate stage incorporated in an XY carriage stage;

FIGS. 9A and 9B are diagrams showing an example of arrangement of thedriving units;

FIGS. 10A and 10B are coordinate systems showing a calculation result ofleakage flux distribution;

FIG. 11A is a diagram illustrating a construction of a one-axis drivingmechanism having an electromagnet unit as a driving source;

FIG. 11B is an explanatory view of a magnetic flux distribution ofelectromagnets;

FIG. 12 is a schematic view showing a construction of acharged-particle-beam exposure apparatus;

FIG. 13 is a block diagram showing a control structure of acharged-particle-beam exposure apparatus; and

FIG. 14 is a block diagram showing overall steps of a semiconductordevice manufacturing process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described indetail in accordance with the accompanying drawings.

First Embodiment

A one-axis electromagnet stage according to the first embodiment is nowdescribed with reference to FIGS. 2A to 4.

FIG. 2A shows a construction of a one-axis driving mechanism having anelectromagnet unit as a driving source. The one-axis driving mechanismshown in FIG. 2A is configured with an I core 200, which is a movablemember, and electromagnets 210 a, 210 b, 210 c and 210 d. Two of theelectromagnets are arranged in each side of the I core in a way tosandwich the I core while maintaining a predetermined gap. Theelectromagnets 210 a, 210 h, 210 c and 210 d are constructed with Ecores 220 a, 220 b, 220 c and 220 d, as well as excitation coils 230 a,and so on, which are wound around the E cores. The four electromagnets210 a, 210 h, 210 c and 210 d are arranged as a stationary member 240relative to the I core 200, and are integrally connected so as not tomake relative movement.

When the I core 200 is driven in the X direction, electric currents ofinverse directions are applied respectively to the excitation coil 230 awound around the E core 220 a of the electromagnet 210 a and theexcitation coil 230 b (FIG. 2B) wound around the E core 220 b of theelectromagnet 210 b to pull the I core 200 in one direction. As aresult, the coils 230 a and 230 b are excited (see FIGS. 3A and 3B).

In order to simultaneously apply the currents of inverse directionshaving the same amount to the excitation coils 230 a and 230 b, theexcitation coils 230 a and 230 b are respectively wound around the Ecores 220 a and 220 b in the directions opposite to each other.Alternatively, the coils may be wound around the E cores in the samedirection, but the polarity of the electric currents applied to theexcitation coils may be inverted by controlling of a current controlcircuit.

FIG. 2B shows a current control circuit 700 which switches the polarityof a current and plural combinations of electromagnets 210 a to 210 hconnected to the circuit 700. The current control circuit 700 controlsthe polarity of current and the amount of current for driving the I core200 in a predetermined direction of the driving axis, thereby causingrespective electromagnets to generate suction power. The magnetic fluxgenerated by the electromagnets is controlled in accordance with thewinding direction of the excitation coils and controlling of the currentcontrol circuit (with respect to the polarity and the amount ofcurrent).

When a magnetic field is formed in the magnetic path from the E cores(220 a to 220 h) to the I core 200, suction power is generated betweenthe E cores (220 a to 220 h) and the I core 200 due to the magneticaction. FIG. 2A shows a state in which the suction power, which iscaused by the magnetic action of the electromagnets 210, acts upon the Icore 200 and the I core is balanced within the gap. In accordance withthe level of suction power, the I core 200 can translationally be drivenin the X(+) direction or X(−) direction.

Next, a distribution of magnetic flux and magnetic field formed aroundthe electromagnet 210 a is described with reference to FIGS. 3A to 3C.FIGS. 3A and 3B are schematic views showing a state of magnetic field ina case where the I core 200 is pulled in the X-axis plus direction (X(+)direction). The electromagnets 210 a and 210 b arranged on the X(+) sideof the I core 200 form a magnetic path in the E cores (220 a, 220 b) andI core 200 as indicated by the arrows with solid lines and generatemagnetic flux. In this stage, currents of inverse directions having thesame amount are applied to the respective excitation coils 230 a and 230b of the electromagnets 210 a and 210 b.

Among the two electromagnets 210 a and 210 b in the X(+) direction, FIG.3A shows the magnetic flux generated by the electromagnet 210 a arrangedin the Z-axis plus direction (Z(+) direction) and FIG. 3B shows themagnetic flux generated by the electromagnet 210 b arranged in theZ-axis minus direction (Z(−) direction). The magnetic path is formedfrom the E cores 220 of the respective electromagnets to the I core 200through the gap as indicated by the arrows with solid lines. Sincecurrents of inverse directions flow through the excitation coils (230 a,230 b) of the electromagnets 210 a and 210 b, the magnetic flux flowingthrough the respective magnetic paths has inverse directions. Suctionpower according to the magnetic flux formed in each magnetic path isgenerated between the I core 200 and electromagnet 210.

In the external space of the E cores 220 a, 220 b and I core 200,leakage flux is generated in the direction indicated by the arrows withdashed lines. The magnetic fields shown in FIGS. 3A and 3B have inversedirections. The leakage flux generated in the external space of therespective electromagnets has inverse polarities and substantially anequal intensity. Since the electromagnets 210 a and 210 b are arrangedin parallel in the same direction (so as to overlap in the Z direction),the magnetic fields having inverse polarities cancel each other, thussuppressing generation of leakage flux around the electromagnets 210 aand 210 b.

By employing the electromagnets utilizing the effect of magnetic fieldcancellation as a driving propulsion source of a one-axis direction, itis possible to construct a one-axis electromagnet stage which can reducethe leakage flux around the electromagnets. Note that a specific exampleof the effect of magnetic field cancellation will be described in thefourth embodiment, so a description thereof is omitted.

The positional relation between the electromagnets (210 a to 210 d) andI core 200 shown in FIG. 2A is described with reference to FIG. 3C. Itis preferable to set the gap (a in FIG. 3C) between the end surface ofthe electromagnets (210 a to 210 d) and the end surface of the I core200 to 2 or 3 mm or less. However, the purpose of the present inventionis not limited to this value. It is acceptable as long as the value a isset sufficiently smaller than the distance (b in FIG. 3C) between thetwo electromagnets (210 a and 210 b, 210 c and 210 d in FIG. 3C)arranged in parallel (overlapped in the Z direction).

The value is so set as a result of consideration of the balance betweenthe intensity of the magnetic flux generated between the respective Ecores (220 a and 220 b, 220 c and 220 d) constituting the electromagnets(210 a, 210 b, 210 c and 210 d) and the intensity of the magnetic fluxgenerated between the electromagnets (210 a to 210 d) and the I core200. In order to generate sufficient suction power, the gap a must besufficiently smaller than the distance b between the electromagnets.

Taking the magnetic path between the E cores 220 a and 220 b of theelectromagnets 210 a and 210 b arranged in the Z direction and themagnetic path of the E cores (220 a, 220B) and the I core 200 satisfyingthe above-described condition for an example, the magnetic fluxgenerated in the magnetic path of the E cores (220 a, 220 b) and the Icore 200 becomes dominant. Therefore, the influence of the magnetic pathbetween the E cores 220 a and 220 b becomes extremely small.

(Construction of Movable Member)

In the above-described construction shown in FIG. 2A, the I core 200pulled by the two electromagnets arranged in the X-axis minus direction(X(−) direction) and the two electromagnets arranged in the X-axis plusdirection (X(+) direction) is constructed with a single common member.However, the I core 200 serving as a movable member does not always haveto be a common member. For instance, as shown in FIG. 4, an I core 401pulled in the X(−) direction and an I core 402 pulled in the X(+)direction may be provided, and they may be integrally connected by an Icore supporting member 403 so that the two I cores do not have relativemovement. The I core supporting member 403 may be formed with a magneticmaterial (e.g., a multi-layer steel plate) or a nonmagnetic material.Adopting a lightweight material as the supporting member 403 enables areduction in weight of the entire movable members (401, 402, 403), thusachieving an advantageous construction for highacceleration/deceleration of the stage and high-speed positioning.

Second Embodiment

A construction of a two-axis electromagnet stage according to the secondembodiment is now described with reference to FIG. 5.

Define that the pairs of electromagnets arranged on both sides of the Icore (total of four electromagnets) are one electromagnet unit.Combining a plurality of electromagnet units as amultiple-degree-of-freedom driving source can construct a multi-axiselectromagnet stage capable of reducing leakage flux around theelectromagnets.

FIG. 5 shows a construction using two sets of electromagnet units 570and 580, which function as a two-axis driving source for translationallydriving an I core in the X-axis direction and rotationally driving the Icore around the Z axis. Electromagnets 510 a to 510 h can generatepredetermined suction power to drive the I core 500 in the translationaldirection (e.g., (X(±) direction). The two sets of electromagnet units570 and 580 are arranged away from each other in the Y-axis direction.For instance, when the electromagnet unit 570 pulls the A-end of the Icore 500 in the X(+) direction and the electromagnet unit 580 pulls theB-end of the I core 500 in the X(−) direction, it is possible to rotatethe I core 500 around the Z axis.

To translationally drive the entire I core 500 in the X(+) direction, apredetermined current is applied to excitation coils 530 a and 530 c ofthe electromagnets 510 a and 510 c as well as excitation coils of theelectromagnets 510 b and 510 d so that suction power in the X(+)direction is generated by the electromagnets 510 a to 510 d arranged onthe X(+) side. In the similar manner, to translationally drive the Icore 500 in the X(−) direction, suction power in the X(−) direction isgenerated on the electromagnets 510 e to 510 h. To rotationally drivethe I core, one end of the I core 500 is pulled in the X(+) directionand the other end of the I core 500 is pulled in the X(−) direction.

The suction power generated by the electromagnets 510 a to 510 h isrealized by a similar mechanism to that of the first embodimentdescribed with reference to FIGS. 3A to 3C, so a detailed descriptionthereof is omitted. For instance, as shown on the electromagnet 510 a, amagnetic path is formed between the E core 520 and I core 500 asindicated by the arrows with the solid lines. Suction power according tothe magnetic flux formed in each magnetic path is generated between theI core 500 and electromagnet 510 a.

In this stage, currents of inverse directions having the same amount areapplied respectively to the excitation coil 530 a wound around theelectromagnet 510 a and the excitation coil 530 b wound around theelectromagnet 510 b. As mentioned in the first embodiment, theapplication of currents in inverse directions may be substituted withinverse winding of the coils or inverse polarities of the currents usingthe current control circuit.

Taking the electromagnet 510 a generating the suction power for anexample, leakage flux such as that shown in FIG. 3A is generated in theexternal space of the E core 520 and I core 500. However, the leakageflux can be cancelled by the electromagnet 510 b arranged in theoverlapping direction because the electromagnet 510 b forms leakage fluxof an inverse polarity and substantially an equal intensity to that ofthe electromagnet 510 a (see FIG. 3B). Accordingly, by employing theelectromagnet units utilizing the effect of magnetic field cancellationas a driving propulsion source of a two-axis direction, it is possibleto construct a two-axis electromagnet stage which can reduce the leakageflux around the electromagnets.

Third Embodiment

A construction of a two-axis electromagnet stage according to the thirdembodiment is now described with reference to FIG. 6.

I cores 660 and 670 are integrally provided to an I core supportingmember 650. Electromagnets 610 a to 610 d are arranged in a way tosandwich the I core 670. The electromagnets 610 a to 610 d generatepredetermined suction power to translationally drive the I core 670 inthe X(±) direction.

For instance, in order to translationally drive the I core 670 in theX(+) direction, a predetermined current is applied to excitation coils630 a and excitation coils of the electromagnet 610 b, thereby causingsuction power in the electromagnets 610 a and 610 b which are arrangedon the X(+) side. To translationally drive the I core 670 in the X(−)direction, a current is applied to cause suction power in theelectromagnets 610 c and 610 d.

Electromagnets 610 e to 610 h are arranged in a way to sandwich the Icore 660. The electromagnets 610 e to 610 h generate predeterminedsuction power to translationally drive the I core 660 in the Y(±)direction.

For instance, in order to translationally drive the I core 660 in theY(+) direction, a predetermined current is applied to excitation coils630 e and 630 f, thereby causing suction power in the electromagnets 610e and 610 f which are arranged on the Y(+) side. Similarly, totranslationally drive the I core in the Y(−) direction, a current isapplied to cause suction power in the electromagnets 610 g and 610 h.

The suction power generated by the electromagnets is realized by asimilar mechanism to that of the first embodiment described withreference to FIGS. 3A to 3C, so a detailed description thereof isomitted. Leakage flux, which is formed when respective electromagnetunits generate suction power, can be cancelled by the combination ofelectromagnets arranged in parallel (overlapped in the Z direction),i.e., 610 a and 610 b, 610 c and 610 d, 610 e and 610 f, 610 g and 610h. Accordingly, by employing the electromagnet units utilizing theeffect of magnetic field cancellation as a driving propulsion source ofa two-axis direction, it is possible to construct a two-axiselectromagnet stage which can reduce the leakage flux around theelectromagnets.

Fourth Embodiment

(Construction of Six-Degree-of-Freedom Stage)

A construction of a six-axis electromagnet stage according to the fourthembodiment is now described with reference to FIGS. 7 to 10. Thesix-axis electromagnet stage according to the fourth embodiment has aconfiguration suitable to a precision-motion substrate stage in acharged-particle-beam exposure apparatus, which mounts a substrate(wafer) and controls the position and posture of the substrate stage forpositioning the substrate at a predetermined position and posture.

FIG. 7A shows a construction of a precision-motion substrate stage. Theprecision-motion substrate stage is a six-degree-of-freedom stagecapable of moving in an optical axis (Z axis) direction, a translational(X and Y axes) direction, a rotational direction around the Z axis (qz),and a rotational direction (tilt direction) around the X axis and Y axis(θx, θy). A wafer 701 is mounted on a substrate holder 703. As a drivingsource for moving the stage in the respective directions of the degreesof freedom, the above-described electromagnet units are provided for sixdegrees of freedom. The bottom plate 710 a and side plate 710 b,mounting the six-degree-of-freedom stage mechanism, functions as aprecision-motion XY stage capable of moving in the X and Y directions,which are orthogonal to the optical axis (Z axis). The combination ofthe bottom plate 710 a and side plate 710 b will be referred to as acenter slider 710 c hereinafter.

Assume that the center slider 710 c is structured on an xy conveyancestage, which is capable of driving on the XY surface at high speed forperforming positioning. The wafer is roughly positioned at high speed bythe xy conveyance stage, and then precisely positioned by theprecision-motion substrate stage according to this embodiment. FIG. 8shows how the above-described precision-motion substrate stage ismounted on the stage base 730 and incorporated in the xy conveyancestage.

Referring to FIG. 7B, numeral 7100 shows a schematic view of the sideplate 710 b seen from the yz plane. A Y movable guide 719 is slidablysupported by virtue of bearings 721 a, provided in the internal portionof an opening 720 a.

Similarly, numeral 7200 shows a schematic view of the side plate 710 bseen from the xz plane. An X movable guide 709 is slidably supported byvirtue of bearings 722 a, provided in the internal portion of an opening720 b.

To move the center slider 710 c in the x direction, thrust in the xdirection is added to the X movable guide 709 to slide the Y movableguide 719 in the opening 720 a, thereby guiding the driving of thecenter slider 710 c in the x direction. To move the center slider 710 cin the y direction, thrust in the y direction is added to the Y movableguide 719 to slide the X movable guide 709 in the opening 720 b, therebyguiding the driving of the center slider 710 c in the y direction.Bearings 731 are provided on the bottom surface of the bottom plate 710a, which faces the top surface of the stage base 730 supporting theentire precision-motion substrate stage 704. When the center slider 710c is driven in the x and y directions, the sliding motion of the slideris guided along the top surface of the stage base 730.

On the top surface of the precision-motion substrate stage 704, asubstrate holder 703 for holding a conveyance target, e.g., a wafer, andX reflection mirror 702 and Y reflection mirror 718 for measuring theposition of the stages are mounted. Using the reflection mirrors, forinstance, a laser interferometer held in a sample chamber (not shown)can measure the position of the substrate stage in the x and ydirections using the internal wall of the chamber as a reference.

Using the same reflection mirrors, the position of the stage is alsomeasured with respect to the rotational direction around the Z axis (θz)and the rotational direction (tilt direction) around the X axis and Yaxis (θx, θy). It is preferable that the measurement of the rotationaldirection and tilt direction be performed from a direction orthogonal tolines of plural beams. With respect to the z direction, an opticalsensor using nonphotosensitive light performs the detection. Avacuum-compliant encoder may be used as a servo sensor.

The precision-motion substrate stage 704 has a cage-like structure tosurround the center slider 710 c. Opening portions 705 and 717 areprovided so that the X movable guide 709 and Y movable guide 719 combineto penetrate the opening portions.

Six movable members (706, 714 to 716) are fixed to the precision-motionsubstrate stage 704. In correspondence with the respective movablemembers, driving units (707, 708, 711 to 713) having the electromagnetunits (FIG. 2A) are fixed to the bottom plate 710 a.

FIG. 7C shows a state in which the Y1 driving unit 712 and Y1 movablemember 715 shown in FIG. 7A are combined. The excitation coil 230 a iswound around the E core 220 a and the excitation coil 230 c is woundaround the E core 220 c, thus constituting the electromagnet 210.Applying a current of a predetermined polarity can generate suctionpower that pulls the Y1 movable member 715 in the Y-axis direction. Inthe electromagnet unit, multiple magnetic shields 790 a and 790 b areprovided. The magnetic shields have opening portions so that the movablemembers (715) can be inserted. The Y 1 driving unit 712 is fixed to thebottom plate 710 a.

FIG. 9A shows an arrangement of stationary members (hatched portions)included in the electromagnet units of the respective driving-axisdirections. The stationary members are arranged in respective positions:three pairs of stationary members for the Z1 electromagnet unit 713, Z2electromagnet unit 711, and Z3 electromagnet unit 720 which generatedriving force in the z direction; stationary members for the X1electromagnet unit 707 which generates driving force in the x direction;and two pairs of stationary members for the Y1 electromagnet unit 712and Y2 electromagnet unit 708 which generate driving force in the ydirection. According to the configuration of this embodiment, theprecision-motion substrate stage 703 can be driven in thesix-degree-of-freedom directions by virtue of the combination of drivingforce in plural directions generated by the plural driving units (707,708, 711 to 713, 720). The arrangement of the respective driving unitsis not limited to the one shown in FIG. 9A. Other arrangements may beadopted as long as the translational driving in the X, Y and Zdirections and the rotational driving around the X, Y and Z axes areachieved by combinations of driving force generated by respectiveelectromagnet unit stationary members.

Multiple magnetic shields (790 a, 790 b in FIG. 7C) formed withPermalloy or the like are provided to the six driving units (707, 708,711 to 713, 720) so as not to cause fluctuation in the magnetic field.It is also preferable that the driving units be arranged sufficientlyfar from the demagnifying electron-optical system and the substrateposition (FIG. 9B) so that leakage flux from the demagnifyingelectron-optical system does not cause fluctuation in the magneticfield. More specifically, it is preferable that the driving units (707,708, 711 to 713, 720) be arranged in a way that a distance (h) from thesubstrate position to the center of gravity G of the center slider 710 cis equal to a distance (h) from the driving unit to the center ofgravity G with respect to the z direction.

(Description of Driving Unit)

The driving unit is configured with the electromagnet unit comprisingthe I core 200 serving as a movable member, four E cores 220 (220 a to220 d) serving as a stationary member, and eight excitation coils, asdescribed in FIG. 2A.

The I core serving as a movable member of the driving unit is fixed tothe precision-motion substrate stage 704 side. Each driving unit isfixed to the center slider 710 c so as not to make relative movement. Byapplying a current of a predetermined polarity to each excitation coil,the two E cores (220 a, 220 b in the case of FIG. 2A) arranged inparallel (overlapped in the Z direction) are excited. As a result, amagnetic path is formed from the E cores (220 a, 220 b) to the I core200 (movable members 714 to 716 in the case of FIG. 7A) through the gap,thus generating magnetic suction power between the E cores and I core.Accordingly, the movable member (I core) can be pulled from the left orthe right (or from the top or the bottom). In other words, the movablemember (I core) can be driven in the plus or minus direction withrespect to one axis. By simultaneously applying currents of inversedirections having the same amount to the excitation coils of therespective E cores, the direction of suction power generated can becontrolled to a certain direction.

As mentioned in the foregoing embodiment, combinations of electromagnetscan cancel the leakage flux in the space around the electromagnets. Thiseffect will be described in detail with reference to FIGS. 10A and 10B.

(Leakage Flux Cancellation Effect)

FIG. 10A shows a calculation result of leakage flux distribution in theneighborhood of the substrate when the respective electromagnet unitsare excited. FIG. 10A shows a case where currents of a uniform directionare applied respectively to the two electromagnets arranged in parallel(overlapped in the z direction). FIG. 10B shows a case where currents ofinverse directions are applied respectively to the two electromagnetsarranged in parallel. FIGS. 10A and 10B show that the absolute value ofthe magnetic field in the neighborhood of the substrate can be reducedto at least 1/10 or less.

(Positional Relation of Cores)

The predetermined gap provided between the end surface of the E core andthe end surface of the I core is actually 2 or 3 mm or less. It ispreferable that the gap be set much smaller than the distance betweenthe two electromagnets arranged in parallel (overlapped in the zdirection). The positional relation between the E cores (220 a and 220b, 220 c and 220 d) and the positional relation between the E cores andI core are set as already described above with reference to FIG. 3C.Taking the magnetic path between the E cores 220 a and 220 b of theelectromagnets 210 a and 210 b, and the magnetic path of the E cores(220 a, 220B) and the I core 200 for an example, the magnetic fluxgenerated in the magnetic path of the E cores (220 a, 220 b) and the Icore 200 becomes dominant according to the foregoing positionalrelation. Therefore, the influence of the magnetic path between the Ecores 220 a and 220 b becomes extremely small.

The structure of the movable members according to the present embodimentis not limited to the integrated one. For instance, plural movablemembers for the plus and minus directions may be provided to themovable-member supporting member as shown in FIG. 4. In this case, thesupporting member integrally supporting the movable members may beformed with a magnetic material or a nonmagnetic material.

In order to generate predetermined suction power in the driving unit, itis necessary to simultaneously apply currents of inverse directionshaving the same amount to, e.g., the excitation coils 230 a and 230 b ofthe electromagnets 210 a and 210 b arranged in the overlappingdirection. The excitation coils 230 a and 230 b may be wound around theE cores 220 a and 220 b in the directions opposite to each other.Alternatively, the coils may be wound around the E cores in the samedirection, but the polarity of the electric currents applied to theexcitation coils may be inverted by controlling of the current controlcircuit 700.

Fifth Embodiment

A one-axis electromagnet stage according to the fifth embodiment isdescribed with reference to FIGS. 11A and 11B.

The one-axis driving mechanism, shown in FIG. 11A, employingelectromagnets as a driving source, is configured with an I core 200,which is a movable member, and electromagnets 210 a to 210 f. Three ofthe electromagnets (210 a, 210 b, 210 c and 210 d, 210 e, 210 f) arearranged in each side of the I core in a way to sandwich the I corewhile maintaining a predetermined gap. The six electromagnets areconstructed with six E cores 220 a to 220 f and excitation coils 230 ato 230 f, which are wound around the E cores. For instance, theexcitation coil 230 a is wound around the E core 220 a, and theexcitation coil 230 d is wound around the E core 220 d as shown in FIG.1 l A. The six E cores 220 a to 220 f and excitation coils 230 a to 230f are arranged as a stationary member, and are integrally connected soas not to make relative movement.

To drive the I core 200 serving as a movable member in the X(+)direction, currents of a predetermined polarity are simultaneouslyapplied to the excitation coils 230 a, 230 b and 230 c of theelectromagnets 210 a, 210 b and 210 c arranged on the X(+) side, therebyexciting the electromagnets. As a result, magnetic flux is generated ina magnetic path from the E cores (220 a, 220 b, 220 c) to the I core 200through the gap, and suction power is generated between the E cores (220a, 220 b, 220 c) and the I core 200 due to the magnetic action.

By virtue of the suction power, the I core 200 can be moved in the X(+)direction. Taking the aforementioned leakage flux cancellation effectinto consideration, currents are applied to the excitation coils so thatthe magnetic flux formed in the respective magnetic path has anidentical direction for the two electromagnets (210 a and 210 c in FIG.11A) positioned in both ends of the three electromagnets arranged in theoverlapping direction (Z direction), and has an inverse direction forthe electromagnet 210 b positioned in the center of the threeelectromagnets (see 1110 to 1130 in FIG. 11B). In this case, themagnetic flux generated by the respective electromagnets is controlledin accordance with the winding direction of the excitation coils, thepolarity of the current controlled by the current control circuit shownin FIG. 2B, and the amount of current (ampere turn).

The three electromagnets on one side of the I core respectively formmagnetic paths from the E cores (220 a, 220 b, 220 c) to the I core 200through the gap. Among the three electromagnets, only the electromagnet210 b positioned in the center has an opposite current direction.Therefore, the magnetic flux flowing through the magnetic path of theelectromagnet 210 b has an inverse direction (1120 in FIG. 11B).Accordingly, the distribution of magnetic field leaking in the spacearound the electromagnet 210 b has an opposite direction to that of theelectromagnets 210 a and 210 c. Since the intensity of the magneticfield is proportional to the amount of current, the intensity of themagnetic field of the magnetic flux formed around the electromagnet 210b needs to be twice as high as that of the magnetic flux formed aroundthe electromagnets 210 a and 210 c.

In other words, assuming that the amount of current (ampere turn)applied by the current control circuit 700 to the electromagnets (210 a,210 c) positioned on both ends is one, the amount of current applied tothe electromagnet 210 b is two. Therefore, the amount of current iscontrolled so that currents are applied simultaneously to the threeelectromagnets arranged in parallel (overlapped in the Z direction) at aratio of 1:2:1 and an inverse current is applied only to theelectromagnet positioned in the center.

Since the excited electromagnets 210 a, 210 b and 210 c are arranged inparallel (overlapping direction) and provided (away from each other) inthe same direction, the magnetic flux distributed in the space aroundthe respective electromagnets overlaps one another. The magnetic fluxfrom the electromagnets 210 a and 210 c positioned on both ends and themagnetic flux from the electromagnet 210 b positioned in the centercancel each other, thereby enabling reduction of the overall leakageflux around the three electromagnets. By virtue of the magnetic fluxcancellation effect, it is possible to achieve a one-axis electromagnetstage having little leakage flux.

In the fifth embodiment, applying currents of a predetermined polarityto the excitation coils 230 a, 230 b and 230 c can be realized bywinding the excitation coils 230 a, 230 b and 230 c around the E coresin the directions opposite to one another. Alternatively, the coils maybe wound around the E cores in the same direction, but the polarity ofthe electric currents applied to the excitation coils may be inverted bycontrolling of the current control circuit 700 (FIG. 2A).

The structure of the movable members according to the present embodimentis not limited to the integrated one. For instance, plural movablemembers for the plus and minus directions may be provided to themovable-member supporting member as shown in FIG. 4. In this case, thesupporting member integrally supporting the movable members may beformed with a magnetic material or a nonmagnetic material. The E cores220 and I core 200 are formed with a magnetic material, such as amulti-layer steel plate.

Adopting a nonmagnetic material as the supporting member enablesreduction in weight of the entire movable members, thus achieving anadvantageous construction for high acceleration/deceleration of thestage and high-speed positioning.

Six Embodiment (Charged-Particle-Beam Exposure Apparatus)

Described next is a charged-particle-beam exposure apparatusincorporating a positioning apparatus employing the electromagnetsdescribed in the first to fifth embodiments as a driving source. FIG. 12is a schematic view showing a construction of a charged-particle-beamexposure apparatus. In FIG. 12, numeral 501 denotes an electron gun,which serves as a charged particle source, and includes the cathode,grid, and anode (not shown). An electron source ES irradiated by theelectron gun is emitted to an electron optical system 503 through anillumination electron optical system 502. The electron optical system503 is configured with an aperture array, a blanker array, an elementelectron optical array unit, or the like, which are not shown. Theelectron optical system 503 forms a plurality of electron source (ES)images. Demagnifying projection is performed on the images by aprojection electron optical system 504, thereby forming electron sourceES images on a wafer 505 serving as an exposure target surface. Apositioning apparatus 508, on which the wafer 505 is placed, isconfigured with a positioning mechanism 507 and a precision motionmechanism 506. The positioning mechanism 507 performs positioning on theplane by moving in the XY direction. The precision motion mechanism 506performs more precise positioning with respect to the positiondetermined by the positioning mechanism 507, and adjusts rotationaldirection of each axis.

For the positioning apparatus 508, the positioning apparatus describedin the aforementioned embodiments is employed. FIG. 13 is a blockdiagram showing a control structure of the charged-particle-beamexposure apparatus.

A control system 1301 controls optical system controllers (1302 to 1304)and a stage driving controller 1305 which controls positioning of thestages. The illumination electron optical system controller 1302controls an illumination electron optical system 1306 based on exposurecontrol data. The electron optical system controller 1303 controls anaperture array 1307, a blanker array 1308, and an element electronoptical system 1309. The projection electron optical system controller1304 controls a deflector 1310 and a projection electron optical system1311.

The stage driving controller 1305 governs the overall positionmeasurement and driving commands for driving the positioning mechanism,and controls the respective electromagnets that drive theprecision-motion substrate stage 704 (FIG. 7A) through the currentcontrol circuit 700.

Also, the stage driving controller 1305 drives the linear motor 1312 tocontrol positioning of the XY conveyance stage on the plane of the stagebase 730.

In controlling the linear motor 1312 and electromagnets 610, the stagedriving controller 1305 detects the stage position data by a laserinterferometer 1313 and feeds back the position data to the controlloop, thereby driving each actuator (610, 1312) and positioning thewafer 701 to a target exposure position corresponding to the exposurecontrol data.

As described above, according to the charged-particle-beam exposureapparatus incorporating the positioning apparatus employing theelectromagnets described in the above-described embodiments as a drivingsource, it is possible to realize highly precise positioning of a wafer.

<Application to a Semiconductor Manufacturing Process>

A semiconductor device manufacturing process (e.g., semiconductor chips,such as an IC or an LSI, CCDs, liquid crystal panels, and the like)employing the above-described charged-particle-beam exposure apparatusis described with reference to FIG. 14.

FIG. 14 shows a flow of an overall semiconductor device manufacturingprocess. In step 1 (circuit design), a circuit of a semiconductor deviceis designed. In step 2, exposure control data of the exposure apparatusis generated based on the designed circuit pattern. Meanwhile, in step 3(wafer production), a wafer is produced with a material such as silicon.In step 4 (wafer process), which is called a pre-process, an actualcircuit is formed on the wafer using the mask and wafer by a lithographytechnique. In step 5 (assembly), which is called a post-process, asemiconductor chip is manufactured using the wafer produced in step 4.Step 5 includes an assembling process (dicing, bonding), a packagingprocess (chip embedding), and so on. In step 6 (inspection), thesemiconductor device manufactured in step 5 is subjected to inspectionsuch as an operation-check test, a durability test, and so on. Thesemiconductor device, manufactured in the foregoing processes, isshipped (step 7).

The aforementioned wafer process in step 4 includes the following steps:an oxidization step for oxidizing the wafer surface; a CVD step fordepositing an insulating film on the wafer surface; an electrode formingstep for depositing electrodes on the wafer; an ion implantation stepfor implanting ions on the wafer; a resist-process step for coating aphotosensitive agent on the wafer; an exposure step for exposing thecircuit pattern on the wafer by the above-described exposure apparatus;a developing step for developing the exposed wafer; an etching step forremoving portions other than the developed resist image; and a resistseparation step for removing the unnecessary resist after the etchingprocess. By repeating the foregoing steps, multiple circuit patterns areformed on the wafer.

By employing the above-described charged-particle-beam exposureapparatus, it is possible to achieve high precision in exposureoperation and improved throughput of the apparatus. Therefore, theproductivity of semiconductor devices can be improved more than by usingconventional productivity techniques.

As has been described above, according to the present invention, leakageflux can be canceled between a plurality of electromagnets by arrangingthe electromagnets in the overlapping direction. As a result, it ispossible to reduce magnetic field fluctuation in the neighborhood of theelectromagnets.

Furthermore, by virtue of the simplified structure, magnetic fieldfluctuation can be reduced. Therefore, it is possible to reduce weightof the precision-motion substrate stage, and realize highacceleration/deceleration of the stage which mounts the precision-motionsubstrate stage, as well as high-speed positioning.

As many apparently widely different embodiments of the present inventioncan be made without departing from the spirit and scope thereof, it isto be understood that the invention is not limited to the specificembodiments thereof except as defined in the claims.

CLAIM OF PRIORITY

This application claims priority from Japanese Patent Application No.2002-318486 filed on Oct. 31, 2002, which is hereby incorporated byreference herein.

1. A positioning apparatus comprising: a movable member for transmittinga driving force in a driving-axis direction to a stage; a firstelectromagnet for driving said movable member in the driving-axisdirection by forming a magnetic path between said movable member andsaid first electromagnet and generating first magnetic flux; and asecond electromagnet, which is positioned away from said firstelectromagnet and arranged in an overlapping direction, for driving saidmovable member in the driving-axis direction by forming a magnetic pathbetween said movable member and said second electromagnet and generatingsecond magnetic flux having an inverted polarity from the first magneticflux. 2-12. (canceled)